Gate valve

ABSTRACT

The invention relates to a gate valve with a housing, having an inlet and an outlet, between which a flow area is arranged, with a sealing insert in the flow area and a sliding element cooperating with a contact area of the sealing insert in the closed state. In a gate valve of this kind, the function must be improved. For this purpose, the sealing insert has a rigid body, which is permanently connected with at least one additional area with a lower rigidity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of and incorporates byreference essential subject matter disclosed in InternationalApplication No. PCT/NO02/00117 filed on Mar. 21, 2002 and German PatentApplication No. 101 14 566.7 filed on Mar. 24, 2001.

FIELD OF THE INVENTION

The invention relates to a gate valve with a housing, having an inletand an outlet, between which a flow area is arranged, with a sealinginsert in the flow area and a sliding element cooperating with a contactarea of the sealing insert in the closed state.

BACKGROUND OF THE INVENTION

A gate valve of this kind is known from U.S. Pat. No. 2,934,313. Thegate valve shown here has a four-part housing with a housing bottompart, on which a housing cover is fixed with bolts. On two sides facingeach other, the housing bottom part and the housing cover form circularopenings, each having a thread. A pipe body with a mating thread can bescrewed onto each of the two threads. All four parts form a flow pipe.The flow cross-section of this pipe can be closed by a sliding element,which can be lowered from the housing cover transversal to the flowdirection of the flow pipe. For sealing the touch areas between thehousing parts and the contact areas between the sliding element and thehousing, the gate valve has a scaling insert made of rubber. The sealinginsert has a tubular shape. Inside the sealing insert, the flowcross-section is substantially limited by metal rings, which areinserted in the sealing insert. The metal rings serve the purpose ofkeeping the flow cross-section inside the sealing insert clear.

U.S. Pat No. 5,279,320 shows a gate valve with a sliding element, whichhas a groove on each side. When opening and closing the gate valve, thesliding element will be guided via the grooves through correspondingtracks on the gate valve housing. The sliding element has aplastic-coated core. In the area of the grooves, the coating of the coreis made of a hard polymer material to reduce the friction. In theremaining areas, in which the sliding element bears on the housing inthe closed state, the coating consists of a soft polymer material. Thisensures a good sealing.

DE 43 25 192 A1 shows a disk gate valve. Here, an assembly anddisassembly in the movement direction of the gate valve is possible. Forthis purpose, the disk gate valve has a sliding housing, which isdivided into a housing top part and a housing bottom part. A sealinglining with a circular opening is built into the sliding housing. When areplacement of the sealing lining is required, the housing top part cannow be removed from the housing bottom part together with the sealinglining. Subsequently, the sealing lining on the housing top part can bereplaced. Further, the sealing lining has a separate cross sealing,which can be removed separately from the remaining sealing lining whendisassembling the disk gate valve.

In operation, for example in utility water systems, gate valves mustensure a reliable closing for a relatively long life (up to 50 years).

SUMMARY OF THE INVENTION

For this purpose, the known gate valves have relatively soft and simplyshaped sealings. These sealings must be relatively tightly fixed in thehousing or applied to the individual elements as coatings. Thus, it isprevented that during operation the sealings can be deformed by theexisting fluid pressure, which will damage them or make them obstructthe free flow. In the known gate valves, with a tubular flow area; thisis therefore substantially limited by housing parts or other supportingelements of a relatively robust material.

The invention is based on the task of improving the reliability of agate valve, in that it provides a gate valve having a housing whichcomprises a bottom part and a top part separated by a flange connection;a first side part comprising a housing inlet and a second side partcomprising a housing outlet; clamping connections between said firstside part and the bottom and top part s and between said second part andthe bottom and top parts, respectively; and a sealing insert clampedbetween said bottom part, said top part and the said first and secondparts; and a sliding member adapted for sliding movement in said housingbetween a first position in which it establishes a gate barrier betweensaid inlet and said outlet and a second position in which said gatebarrier is removed, said sealing insert having an opening opposing saidinlet and said outlet, and further having a contact area adapted forsealing contact with said sliding member during said member's slidingmovement between said positions, said sealing contact establishing saidbarrier when said sliding member is in said first position. The inventedgate valve is characterized in that the sealing insert comprises a rigidbody permanently connected to areas having less rigidity than said rigidbody, said areas with less rigidity including said contact area andclamped areas in said flange connection and areas clamped between saidfirst side part and the bottom and top parts and between said secondside part and the bottom and top parts.

The insert according to the invention is thus intended for assembly in agate valve housing having an inlet and an outlet, between which a flowarea is arranged, said valve insert comprising a tubular part arrangedin the flow area and adapted for receiving of a sliding element. Theinsert is characterized in that the tubular part comprises a rigid bodyof which at least a portion is adapted for sealing engagement with aportion of said sliding element and permanently connected to a materialof a rigidity less than that of said rigid body.

It must be stressed that the term “sealing insert” describes anindividual element, which can also be handled independently of the othercomponents of the gate valve. The additional area partly alsoaccomplishes a sealing function and can thus, for convenience, also becalled sealing area.

The rigid body makes it possible to give the sealing insert almost anydesired shape and size, without requiring stabilisation throughadditional supporting arrangements. For example, a sealing insert ofthis kind can also have large openings or a tubular shape, whose freecross-section is kept open by the rigidity of the sealing insert. Thus,it is possible to use a large variety of sealing insert shapes. Thesealing inserts can also have relatively complex shapes. This newlyacquired freedom in the use of sealing inserts now makes it possible todevelop large inner areas of the gate valve by means of a correspondingsealing insert. In this connection a material can be used for thesealing insert, which is more easily and accurately workable than thehousing of the gate valve. In this way, different areas of the gatevalve can be made with a higher accuracy and also more easily.Especially in areas, which cooperate with the sliding element, thisimproved accuracy is a large advantage. Exactly here, the sealing insertcan give an improved sealing and a reduced material wear. The remainingareas can still be made of robust materials, like for example cast.Further to the exact shapability of the sealing insert, the additionalarea with the reduced rigidity can also provide a good sealing indesired areas. It is no longer required to provide separate sealings. Onthe contrary, a sealing is formed by sections or areas of the additionalarea with reduced rigidity, which forms one unit with the more rigidbody. Additionally, the one-unit embodiment of the rigid body and theadditional area causes a substantial simplification of the assembly.Further, the permanent connection ensures improved scaling properties ofthe sealing insert. The connection may, for example, be achieved throughbonding.

It is particularly advantageous that the permanent connection occurs onthe molecular level. This ensures an optimum connection between theindividual areas of the sealing insert. Thus, the sealing properties ofthe sealing insert are improved.

It is favourable that the sealing insert has a plastic material. The useof the plastic material ensures a simple and exact working of thesealing insert. Further, the use of a plastic material reduces themanufacturing costs of the sealing insert.

It is advantageous that the plastic material has a rigid and a softmaterial component, the rigid body being formed substantially by therigid material component and the additional area being formedsubstantially by the soft material component. This use of two materialcomponents of plastic material provides a good connection between thedifferent areas of the sealing insert. Thus, the sealing properties ofthe sealing insert are improved. Further, in this way also relativelycomplex shapes of the sealing insert can be made relatively easily andexactly.

Further, it is favourable that the rigid material component is made ofpolyoxymethylene (POM). The use of this plastic material enables a highdegree of accuracy during production of the sealing insert. A subsequentworking of a sealing insert made of this plastic material can be limitedto a trimming.

It is advantageous that the soft material component is made ofethylene/propylene diene monomer (EPDM). The use of this plasticmaterial gives additional areas with a high flexibility. Thus, again, arelatively good sealing can be achieved.

In a further advantageous embodiment, a filling material is arrangedbetween the sealing insert and the housing. Through the use of such afilling material, the retaining of the sealing insert in the housing canbe optimised. Thus, possible deformations of the sealing insert duringoperation can be reduced. Further, the filling material provides a goodsealing between the sealing insert and the housing, so that here slackwater cannot gather.

In a further or alternative embodiment it is ensured that the sealinginsert is provided with holes. Through these holes, water can penetrateto an area between the sealing insert and the housing. Usually, thepenetration of water can never be completely avoided. When no additionalmeasures are taken, there is a risk that the water remains there andthat, for example, microorganisms may develop. Particularly whencontrolling drinking water with a gate valve, this is not desired and inmany cases also not permitted. When now holes are provided in thesealing insert, a permanent water circulation can be achieved, that is,the risk that areas with slack water are formed, in whichmicro-organisms can develop, is substantially reduced. The tightness ofthe valve is, however, not influenced by the holes.

It is preferred that the holes are arranged in the guiding part. Here,the risk of creation of dead zones between the housing and the sealinginsert, in which water can gather, is highest. When the holes arearranged in the guiding part or at least mainly in the guiding part, therisk of creation of dead zones in the guiding part is reduced.

It is advantageous that the sealing insert has at least one clampingarea, which can be clamped between at least two housing parts of thehousing. For example, it is here possible that such a clamping area ofthe additional area is inserted in a groove or any other recess, whoseshape corresponds to that of the clamping area. A correspondingcomponent of another housing part will then compress the clamping areain the groove when joining the two housing parts. In this way arelatively good sealing between two housing parts can be achieved.Further, such a clamping area in the compressed state ensures a saferetaining of the sealing insert in the housing. Additionally, therecesses made in accordance with the clamping area ensure an exactpositioning of the sealing insert during assembly.

Further, it is favourable that the clamping area has a clamping lip,which can be clamped between a top part and a bottom part of thehousing. Here, it can, for example, be imagined that when fixing the toppart on the bottom part via a flange connection, such a clamping lip isclamped in the flange surface. Here, the clamping lip may also haveholes for leading through bolts. This ensures a safe sealing between thetop part and the bottom part of the housing. Further, during assembly,such a clamping lip can make the positioning of the sealing insert inthe housing easier.

It is favourable that the clamping area has a clamping ring, which canbe clamped between the top part or the bottom part of the housing and aninlet part or an outlet part of the housing. Thus, when mounting aninlet or an outlet part on the remaining housing, a safe sealing can beachieved in the corresponding inlet or outlet area.

Preferably, the clamping collar is inserted in a V-shaped groove, inwhich a V-shaped mounting collar engages radially in relation to theinlet or the outlet part. Thus, in relation to the flow area, theclamping collar extends under an angle, thus engaging in this groove.When now the mounting collar with its corresponding V-shaped embodimentengages in the groove, the clamping collar is not only retained in thegroove, it is also to a certain extent clamped. Thus, on the one hand,the required forces for retaining the sealing insert in the housing in asafe manner are provided. On the other hand, the tightness between theinlet part or the outlet part, respectively, and the housing insert isrealised with relatively simple measures.

It is preferred that in the area of the groove bottom the clampingcollar has a thickening. In a manner of speaking, an O-ring sealing thenoccurs, which further improves the tightness. Through a compression ofthe thickened area of the clamping collar it is ensured that theclamping collar is sealed on the full circumference of the connectionbetween the inlet or the outlet part and the housing.

Preferably, the clamping collar has notches on its extreme end. Theextreme end is the end, which is not connected with the housing insert.Through the special embodiment with the V-shaped groove, into which theclamping collar is pressed radially outward, an area of the clampingcollar occurs, which is led radially inward again. The notches nowensure that in spite of the reduced diameter the clamping collar doesnot fold, which would cause problems with the tightness.

It is preferred that the notches extend right down to the groove bottom.With this embodiment it is ensured that no areas occur, in which toomuch material of the clamping collar is available, which couldeventually fold.

It is advantageous that the contact area is formed, at least partly, bythe additional area. In this way, also the contact area has a relativelyflexible embodiment. In the closed state of the gate valve, a goodsealing between the sliding element and the sealing insert can thus beensured.

It is also favourable that the contact area is adapted to the shape ofthe sliding element. Such an adaptation ensures a good cooperationbetween the bearing area and the sliding element. Thus, an improvedsealing can be achieved.

It is particularly favourable that the sealing insert has a guidingpart, in which the sliding element can be guided. In this way also theareas of the gate valve cooperating low material with the slidingelement can be made relatively accurately. Thus, a good sealing and alow material wear can be achieved.

It is advantageous that the guiding part branches off from the remainingsealing insert into a control area in the top part of the housing, inwhich the sliding element is arranged in the open state. Thus, it isachieved that in any position the sliding element is guided by theguiding part over a long distance. Further, in this way, the total area,in which the sliding element is moving, can be formed by the sealinginsert. As a result, this gives a particularly exact guiding of thesliding element and a good sealing.

It is also advantageous that the guiding part has a guiding device,which cooperates with at least one guiding counter-part of the slidingelement. With such a guiding device an exact guiding of the slidingelement in exactly synchronised areas can be realised. In this way alower wear and a good sealing can be achieved. The guiding counter-partcan, for example, be an element with straight edges, which cooperatewith corresponding edges of a guiding groove of the guiding device.

Further, it is favourable that the guiding device is formed by the rigidbody. This gives a relatively low friction between the guiding deviceand the sliding element.

Further, it is advantageous that the outside of the guiding part hasribs, which are formed by the rigid body. Such ribs ensure a stable holdof the guiding part in the housing. Thus, an exact guiding of thesliding element can be ensured at any time.

It is also favourable that the complete guiding part is formed by therigid body. This increases the stability of the guiding part, whichensures a stable operation of the gate valve.

Preferably, the rigid body has a glass fibre reinforcement. Areinforcement by means of glass fibre gives the rigid body a highermechanical loadability. In other words, it can stand higher forces. Thishas a positive influence on the life of the sealing insert.

It is particularly preferred that the additional area covers at least50% of the surface of the rigid body, which gets in touch with water.Thus, on the major part of the surface the additional area ensures thatthe flowing water does not release glass fibres from the rigid body.Thus, the sealing insert is also suited for drinking water.

Further, this task is solved by a method for the manufacturing of asealing insert for a gate valve as described above, in which an at leasttwo-stage casting process is carried through. Thus, it is possible tomanufacture individual areas of the sealing insert separately with ahigh accuracy.

Preferably, the rigid body is manufactured in a first stage and theadditional area in a second stage. With such a manufacturing method, thevarious areas of the sealing insert are adapted optimally to each other.Thus, the sealing properties of the sealing insert can be furtherimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is described on the basis of a preferredembodiment in connection with the drawings, showing:

FIG. 1 a partial section through a gate valve according to the state ofthe art,

FIG. 2 a partial section through a gate valve according to theinvention,

FIG. 3 an exploded view of the gate valve according to FIG. 2,

FIG. 4 a partial section through a sealing insert of the gate valveaccording to Fig. 2 and 3,

FIG. 5 an exploded view of the sealing insert according to FIG. 4,

FIG. 6 a modified version of a sealing insert,

FIG. 7 a partial section through a gate valve with the modified sealinginsert,

FIG. 8 an enlarged sectional view “X” from FIG. 7,

FIG. 9 an exploded view of the sealing insert according to FIG. 6

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The gate valve 1 according to the state of the art, shown in Fig. 1, hasa housing 2, which typically consists of cast iron coated with epoxyresin. The housing 2 has an inlet 3 and an outlet 4, and between them aflow area 5. Movable into the flow area is a sliding element 6, whichcan be controlled by a spindle 7. For this purpose, a control area 8branches off from the flow area 5 in the shape of a T-piece, in whichcontrol area 8 the sliding element 6 is guided and a part of the spindle7 is arranged.

In the open state of the gate valve 1, the sliding element 6 is arrangedin the control area 8 of the housing 2. In the closed state of the gatevalve 1, the sliding element 6, however, bears on the housing 2 in acontact area 9 in the flow area 5.

The sliding element 6 has a metal core, which is coated with an elastic,vulcanised rubber. In this connection, the coating on two sides of thesliding element 6 cooperates with edges, which project from the housing2.

Particularly the manufacturing of the areas of the housing 2, whichcooperate with the sliding element 6, causes large problems. This isparticularly the case, when cast iron is used as material for thehousing 2. Tolerances between the housing 2 and the sliding element 6may occur, which can lead to leakages of the gate valve 1.

FIG. 2 shows a gate valve 1 according to the present invention. Here,the elements, which correspond to the embodiment according to the stateof the art shown in FIG. 1, have the same reference numbers.

Also here, the housing 2 of the gate valve 1 has an inlet 3, an outlet 4and between them a flow area 5. The housing 2 is built up of fourhousing parts. The flow area 5 is surrounded by a bottom part 10 and atop part 11, which are connected with each other in two sections via aflange arrangement 12. When dismounting the top part 11 from the bottompart 10, the flow area 5 is thus freely accessible, for example forcleaning or control purposes. Further, an inlet part 13 and an outletpart 14, respectively, are arranged at the inlet 3 and the outlet 4. Allhousing parts 10, 11, 13, 14 are made to be corrosion resistant. Thismeans that they have a corresponding surface coating or that they aremade of a suitable material. As surface coating, epoxy resin is suited.

With the gate valve 1 shown here, the flow through the flow area 5 canbe controlled via a sliding element 6, which is controlled via a spindle7. For this purpose, the sliding element 6 can be moved out of thecontrol area 8 in the top part 11 of the housing 2 into the flow area 5.The sliding element 6 is made of cast iron. Other materials, like forinstance stainless steel, brass or plastic can also be used.

In the open state of the gate valve 1, the sliding element 6 is, asknown also from the state of the art, arranged in the control area 8. Inthe closed state of the gate valve 1, the sliding element 6 bears in acontact area 9. In this connection, this contact area 9 is made on asealing insert 15.

The sealing insert 15 is made in a T-shape, and it can be inserted inand dismounted from or replaced in the gate valve 1, independently ofall other components of the gate valve 1. The sealing insert 1 has atubular part 16, from which a guiding part 17 branches off. The tubularpart 16 is arranged in the flow area 5, whereas the guiding part 17projects into the control area 8. In order to ensure a safe retaining ofthe sealing insert 15 in the housing 2, the outer shape of the sealinginsert 15 is adapted to the areas of the housing 2, on which it bears.Further, a filling material (not shown) can be provided between thehousing 2 and the sealing insert 15. In this way, the sealing insert 15can be made to fit even better into the housing 2.

Further, a good retaining of the sealing insert 15 in the housing 2 isachieved by means of clamping areas 18, 19. In the present embodiment,these are made by means of clamping lips 18 and clamping collars 19. Inthe assembled state of the gate valve 1 shown here, each clamping area18, 19 of the sealing insert 15 is clamped between two or three housingparts 10, 11, 13, 14 of the housing 2. Here, the clamping of theclamping lips 18 occurs in the flange arrangement 12 by means of aflange surface 20 a, 20 b on the bottom part 10 and the top part 11,respectively. The clamping collar 19, however, is clamped in a groove21, which is made in both the bottom part 10 and the top part 11 in thearea of the inlet 3 and/or the outlet 4. Together with the clampingcollar 19, a mounting collar of the corresponding inlet part 13 oroutlet part 14 is arranged in the groove 21. After the assembly, thismounting collar 22 presses on the clamping collar 19, which is thusclamped between the mounting collar 22 and an inner groove wall 23.

Further, the guiding part 17 of the sealing insert 15 has a guidingdevice 24. Via this guiding device, the sliding element 6 is guidedduring displacement. The guiding device 24 of the guiding part 17cooperates with a guiding counter-part, which is arranged on the slidingelement 6. In the embodiment shown, this guiding counter-part 25 is madeof approximately rectangular projections, which are arranged on bothsides of the sliding element 6. Of course, it is also possible for theguiding device 24 and the guiding counterpart 25 to have any other knownand suited shape.

FIG. 3 shows an exploded view of the gate valve 1 according to theembodiment in FIG. 2. It clearly shows the four housing parts of thehousing 2, namely the bottom part 10, the top part 11, the inlet part 13and the outlet part 14. Further, bolts 26 are shown, with which thebottom part 10 can be mounted on the top part 11. One advantage of sucha four-part housing 2 is that providing a corresponding inlet part 13and outlet part 14 makes the gate valve 1 adaptable to differentconnection forms. In the embodiment shown, both the inlet part 13 andthe outlet part 14 have a flange part 27. Alternatively, the inlet part13 and the outlet part 14 can have connecting parts of any other knownor suited connection form. Possible are, for example, connecting partsof a plug-in or screwed connection. Further, an inlet part 13 or anoutlet part 14 can be provided, which can be connected via a bush with aline, preferably made of polyethylene (PE). For this purpose, the bushcould, for example, have an area, which can be welded onto the PE-line.Further, also a simple tube end can be used for any known weldingconnection. Besides, the inlet part 13 or the outlet part 14 can be madeas a T-piece or any other known shape.

Further, the sealing insert 15 can be seen. The guiding device 24 of thesealing insert 15 has a guiding groove 28 with a square cross-section.This guiding groove 28 cooperates with the guiding counter-part 25 ofthe sliding element 6.

Additionally, ribs 29 are arranged on the outside of the guiding part17. On the one hand, they ensure that in the control area 8 the guidingpart 17 bears safely on the top part 11 of the housing 2. On the otherhand, the ribs 29 increase the stability of the guiding part 17.

When assembling the gate valve 1, the sealing insert 15 is first placedin the bottom part 10 of the housing 2. The clamping lips 18 and theclamping collar 19 are arranged at the flange surfaces 20 a, 20 b andthe grooves 21, respectively, provided for this purpose, which ensuresan exact positioning of the sealing insert 15 in relation to the bottompart 10. Then the mounting collars 22 of the inlet part 13 and theoutlet part 14 are inserted in the groove 21. Now, on these first threehousing parts 10, 13, 14 of the housing 2, the top part 11 is mounted,in which the sliding element 6 and the spindle 7 have already beenmounted. On both sides of the sliding element 6, the guidingcounterparts 25 are inserted in the guiding grooves 28 of the guidingdevice 24 of the sealing insert 15. Then, the top part 11 and the bottompart 10 are tightened to each other by means of bolts 26. Finally, thegate valve 1 can be mounted in a fluid circuit, for example a utilitywater system, by means of the flange parts 27 of the inlet part 13 andthe outlet part 14, respectively.

For the control of a flow, the gate valve 1 can now be opened or closed.For this purpose, the sliding element 6 is displaced by means of thespindle 7. For the operation of the spindle 7, the gate valve 1 has onits top part 11 a control connection 30. A handwheel, a motor or anyother known and suited operating device can be connected to this controlconnection 30.

FIG. 4 shows a partial section through the sealing insert 15. It can beseen from the cut surfaces that the sealing insert 15 consists of twoparts, namely a rigid body 31 (widely hatched) and an additional area 32(tightly hatched). In the contact area 9, the additional area 32 alsoassumes sealing tasks in cooperation with the sliding element 6, and cantherefore also be called sealing area. The sealing insert 15 is made ofa plastic material, the plastic material having in the area of the rigidbody 31 a rigid material component and in the additional area 32 a softmaterial component. In a preferred manner, the rigid material componentconsists of polyoxymethylene (POM) and the soft material component ofethylene/propylene diene monomer (EPDM). Both material components of therigid body 31 and the additional area 32 are connected with each otherin the connecting areas 33 on the molecular level.

In the embodiment shown, the rigid body 31 extends over the completesealing insert 15. Here, the complete guiding part 17 is exclusivelyformed by the rigid body 31.

Particularly in the area of the guiding device 24 this is veryimportant, to ensure that the displacement of the sliding element 6causes as little friction as possible. The clamping lips 18 and theclamping collar 19, on the other hand, are formed by the additional area32. In this way, the use of the soft material component ensures a gooddeformability of these clamping areas 18, 19. In the assembled state ofthe gate valve 1 a better sealing can thus be achieved between theindividual parts 10, 11, 13, 14 of the housing 2.

The additional area 32 is also arranged in the contact area 9, withwhich the sliding element 6 cooperates in the closed state of the gatevalve 1. With the good deformability of the contact area 9, which isobtained by this, a better sealing between the sliding element 6 and thesealing insert 15 is achieved. Additionally, the shape of the contactarea 9 is adapted to the sliding element 6. In the area cooperating withthe contact area, the sliding element 6 has an approximate V-shape. Alsothe adaptation of the contact area 9 to this V-shape ensures a goodsealing in the closed state of the gate valve 1.

FIG. 5 shows the rigid body 31 and the additional area 32 in separateviews. The sealing insert 15 shown is manufactured in a two-stagecasting process. Preferably, the rigid material component required forthe manufacturing of the rigid body 31 is fed into a casting mould. Thesoft material component of the additional area 32 is subsequentlymoulded on to the rigid body 31 thus appearing. In order to achieve acomplete distribution of the soft material component across the intendedareas during the second moulding process, distribution flutes are formedon the rigid body 31 during the first moulding process. By means of thismanufacturing process, the rigid body 31 and the additional area 32 ofthe sealing insert 15 are optimally adapted to and fixedly connectedwith each other. The additional area 31 is arranged both inside andoutside the rigid body 31.

The FIGS. 6 to 9 show a modified embodiment of a sealing insert 15. Sameparts have the same reference numbers as in FIGS. 1 to 5.

One change is that the sealing insert 15 is provided with openings 51,52, through which water or another fluid controlled by the gate valvecan enter an area between the sealing insert 15 and the housing 2. Theopenings 51 are arranged in the guiding part 17. The openings 51 arearranged at the lower end of the guiding part 17, shortly above theclamping lips 18. The openings 51, 52 penetrate both the rigid body 31and the additional area 31. They can be produced already during themoulding of the sealing insert 15. However, it is also possible to makethem later, for example by means of boring or milling.

With regard to the rigid body 31, the opening 52 arranged in such a waythat it is situated between the ribs 29. Therefore it is difficult tosee in FIG. 9.

In a manner not shown in detail, the rigid body 31 is made of a plasticmaterial, which is reinforced with glass fibres. Instead of glassfibres, other sorts of reinforcement fibres can be used, for examplecarbon fibres. The additional area 31 is made in such a way that itcovers at least 50% of the surface of the rigid body 31, which gets intouch with the water flowing through the gate valve 1. In the surfaces,which are covered by the additional area 31, a contact between the waterand the glass fibre reinforced plastic material is avoided, whichimproves the opportunity of avoiding the risk that glass fibres arewashed out of the plastic material of the rigid body 31.

As can be seen from the FIGS. 7 and 8, the design of the clamping collar19 has also been changed. The clamping collar 19 forms a “tubular”extension of the flow area 5. In a part 60 of the extension, it expandsin a cone shape, that is, the diameter increases in this part 60. In asecond part 61 the extension has a substantially constant diameter.

The clamping collar 19, possibly having a somewhat smaller thicknessthan, but being made in one piece with the additional area 32, isinserted in a V-shaped groove 53 on the bottom part 10 and the top part11, and is here retained by a circumferential, V-shaped projection onthe inlet part 13. A corresponding embodiment, not shown in detail, isavailable on the outlet part 14. The clamping of the clamping collar 19between the top part 11 and the inlet part 13 and likewise between thebottom part 10 and the inlet part 13, prevents contact between the parts11 and 13 and also between the parts 10 and 13. Thus, a damage of apossible coating (for example epoxy resin) of the parts 10, 11, 13, 14is prevented. The same consideration also applies for the outlet part14.

In the area of the groove bottom of the groove 53, the clamping collar19 is thickened, that is, has a thickening 55, which forms some sort ofan O-ring seal. It is not absolutely required that during mounting ofthe inlet part 13 on the housing 10, 11 the thickening 55 is compressedat the deepest spot of the groove 53. However, the thickening 55 isshaped so that an extensive bearing of the clamping collar 19 is ensuredon both the inlet part 13 and on the bottom part 10 or the top part 11,respectively, of the housing 2.

As appears particularly from the FIGS. 6 and 9, the clamping collar 19has notches 56, which are arranged in the circumferential direction. Ascan be seen from FIG. 8, the clamping collar 19 is led radially inwardagain outside the groove bottom of the groove 53. If not for the notches56, there would be a risk that folds could appear, which again couldinfluence the tightness of the connection between the inlet part 13 andthe housing 2. Through the notches 56, this risk no longer exists.

With the embodiment of the clamping collar 19 shown in FIG. 8, anexcellent tightness of the sealing insert 15 in the housing 2 appears.When the inlet part 13 with its projection 54 is inserted in the groove53, the clamping collar is strained. At the same time, the clampingcollar 19 is compressed in the area of the thickening 55. This ensures atight transition between the inlet part 13 and the sealing insert 15.

1. A gate valve having a housing comprising a bottom part and a top partseparated by a flange connection; a first side part comprising a housinginlet and a second side part comprising a housing outlet; clampingconnections between said first side part and the bottom and top partsand between said second part and the bottom and top parts, respectively;and a sealing insert clamped between said bottom part, said top part andthe said first and second parts; and a sliding member adapted forsliding movement in said housing between a first position in which itestablishes a gate barrier between said inlet and said outlet and asecond position in which said gate barrier is removed, said sealinginsert having an opening opposing said inlet and said outlet, andfurther having a contact area adapted for sealing contact with saidsliding member during said member's sliding movement between saidpositions, said sealing contact establishing said barrier when saidsliding member is in said first position, said gate valve beingcharacterized in that: the sealing insert comprises a rigid bodypermanently connected to areas having less rigidity than said rigidbody, said areas with less rigidity including said contact area andclamped areas in said flange connection and areas clamped between saidfirst side part and the bottom and top parts and between said secondside part and the bottom and top parts.
 2. A gate valve according toclaim 1, wherein said permanent connection is on a molecular level.
 3. Agate valve according to claim 1, wherein said sealing insert comprises aguiding part for said sliding member extending in said top part.
 4. Agate valve according to claim 1, wherein the sealing insert comprises aplastic material.
 5. A gate valve according to claim 4, wherein theplastic material has a rigid and a soft material component, the rigidbody being formed substantially by the rigid material component and theareas having less rigidity being formed substantially by the softmaterial component.
 6. A gate valve according to claim 5, wherein therigid material component is made of polyoxymethylene (POM).
 7. A gatevalve according to claim 5, wherein the soft material component is madeof ethylene/propylene diene monomer (EPDM).
 8. A gate valve according toclaim 1, wherein a filling material is arranged between the sealinginsert and the housing.
 9. A gate valve according to claim 1, whereinthe sealing insert is provided with holes.
 10. A gate valve according toclaim 9, wherein the holes are arranged in the guiding part.
 11. A gatevalve according to claim 1, wherein the sealing insert has at least oneclamping area, which can be clamped between at least two housing partsof the housing.
 12. A gate valve according to claim 11, wherein theclamping area has a clamping lip, which can be clamped between the toppart and the bottom part of the housing.
 13. A gate valve according toclaim 11, wherein the clamping area has a clamping collar, which can beclamped between the top part or the bottom part and the first side partor the second side part of the housing.
 14. A gate valve according toclaim 13, wherein the clamping collar is inserted in a V-shaped groove,in which a V-shaped mounting collar engages radially in relation to theinlet or the outlet.
 15. A gate valve according to claim 14, wherein inthe area of the groove bottom of the groove the clamping collar has athickening.
 16. A gate valve according to claim 13, wherein the clampingcollar has notches on its extreme end.
 17. A gate valve according toclaim 16, wherein the notches extend right down to the groove bottom.18. An insert for assembly in a gate valve housing having an inlet andan outlet, between which a flow area is arranged, said valve insertcomprising a tubular part arranged in the flow area and adapted forreceiving a sliding element, wherein the tubular part comprises a rigidbody of which at least a portion is permanently connected to a materialof a rigidity less than that of said rigid body for sealing engagementwith a portion of the sliding element, wherein said permanent connectionis on a molecular level.
 19. An insert for assembly in a gate valvehousing having an inlet and an outlet, between which a flow area isarranged, said valve insert comprising a tubular part arranged in theflow area and adapted for receiving a sliding element, wherein thetubular part comprises a rigid body of which at least a portion ispermanently connected to a material of a rigidity less than that of saidrigid body for sealing engagement with a portion of the sliding element,wherein the insert comprises a plastic material, and wherein the plasticmaterial has a rigid and a soft material component, the rigid body beingformed substantially by the rigid material component and the material ofa rigidity less than that of the rigid body being formed substantiallyby the soft material component.
 20. An insert according to claim 19,wherein the rigid material component is made of polyoxymethylene (POM).21. An insert according to claim 19, wherein the soft material componentis made of ethylene/propylene diene monomer (EPDM).
 22. An insertaccording to claim 18, wherein a filling material is provided and isconfigured to be arranged between the insert and the housing.
 23. Aninsert according to claim 18, wherein the insert is provided with holes.24. An insert according to claim 23, wherein the holes are arranged in aguiding part, in which the sliding element can be guided.
 25. An insertaccording to claim 18, wherein the insert has at least one clampingarea, which can be clamped between at least two housing parts of thehousing.
 26. An insert according to claim 25, wherein the clamping areahas a clamping lip, which can be clamped between a top part and a bottompart of the housing.
 27. An insert according to claim 25, wherein theclamping area has a clamping collar, which can be clamped between a toppart or a bottom part and the inlet or the outlet of the housing.
 28. Aninsert according to claim 27, wherein the clamping collar is configuredto be inserted in a V-shaped groove and to be held in place by aV-shaped mounting collar which engages the V-shaped groove radially inrelation to the inlet or the outlet.
 29. An insert according to claim28, wherein, in the area of the groove bottom of the groove into whichthe clamping collar is configured to be inserted, the clamping collarhas a thickening.
 30. An insert according to claim 27, wherein theclamping collar has notches on its extreme end.
 31. An insert accordingto claim 30, wherein the notches are configured to extend right down toa groove bottom into which the clamping collar is configured to beinserted.
 32. A sealing insert for use with a gate valve having asliding member and a housing including a bottom part and a top partseparated by a flange connection, a first side part including a housinginlet, a second side part including a housing outlet, clampingconnections between the first side part and the bottom and top parts andclamping connections between the second part and the bottom and topparts, respectively, the sliding member adapted for sliding movement inthe housing between a first position in which it prohibits a flowbetween the housing inlet and the housing outlet and a second positionin which a flow between the housing inlet and the housing outlet is notprohibited, the sealing insert comprising: an opening adapted toaccommodate sliding movement of the sliding member of the gate valve;and a rigid body permanently connected to areas having less rigiditythan said rigid body, said areas with less rigidity including a contactarea adapted for sealing contact with the sliding member of the gatevalve and clamped areas adapted to be clamped in said flange connectionand adapted to be clamped between said first side part and the bottomand top parts and between said second side part and the bottom and topparts.
 33. A sealing insert according to claim 32, wherein the sealinginsert comprises a plastic material.
 34. A sealing insert according toclaim 32, wherein the plastic material has a rigid and a soft materialcomponent, the rigid body being formed substantially by the rigidmaterial component and the areas having less rigidity being formedsubstantially by the soft material component.
 35. A sealing insertaccording to claim 34, wherein the rigid material component is made ofpolyoxymethylene (POM).
 36. A sealing insert according to claim 34,wherein the soft material component is made of ethylene/propylene dienemonomer (EPDM).
 37. A sealing insert according to claim 32, wherein theclamping areas adapted to be clamped between said first side part andthe bottom and top parts and between said second side part and thebottom and top parts each have a clamping collar, which can be clampedbetween the top part or the bottom part and the first side part or thesecond side part.
 38. A sealing insert according to claim 37, whereinthe clamping collar is inserted in a groove, in which a mounting collarengages radially in relation to the housing inlet or the housing outlet.